FIELD OF THE INVENTION
The invention relates to a wafer frame for accommodating disk-shaped thin semiconductor wafers, which generally have a round structure. Such wafer frames, in which wafers have been fitted, are conveyed, for example, in a cassette one above the other in trays and are fed to appropriate treatment stations.
For example, photolithographic and etching structuring work is carried out on semiconductor wafers, to produce semiconductor chips. A multiplicity of semiconductor chips are present on a wafer. During the structuring work on the wafer, active regions on the wafer, which later form the individual chip, are spaced apart by a predetermined grid, so that zones or lines are produced along which the wafer can be cut. A process which is customarily used for that purpose is what is known as abrasive cutting using a high-speed diamond wheel.
In order to carry out that process, the wafer is held and guided in an accurate position using a vacuum device. For that purpose, a wafer frame is initially covered on the top side with a film. The wafer is placed with its unstructured side downward on the top of the film. That prevents mechanical damage to the individual chips which are present after the cutting. The vacuum device is applied to the film centrally from below through a central passage of the wafer frame, and the wafer or wafer and film are sucked on and locked in place. The cutting depth during the abrasive cutting is selected in such a way that the wafer is approximately or entirely cut through and the cutting depth penetrates slightly into the film.
The diameters of the wafers are being constantly increased in order to optimize the production processes as a whole. While previously the diameters were 4, 5 or 6 inches, nowadays wafers with a diameter of 8 inches are being used (1 inch=2.54 cm). Thus it is necessary to convey and treat wafers with a diameter of approximately 200 mm. Heretofore, in microelectronics mounting technology a metal wafer frame has been used to fix and handle such wafers.